When living and working in a high noise environment, the environmental noise harms human health greatly, and at the same time, high noise may have influence on the capability to distinguish useful sound signals from noise. Therefore, an electrical device, which can attenuate noise and receive sound signals clearly, is required. At present, an existing source noise-suppressing receiver has some shortcomings.
The scheme disclosed in U.S. Pat. Nos. 5,889,875 and 5,917,923, two series acoustic chambers can suppress the influence of the distance from the noise source direction in the noises input from every sound inlet, thus making the noise picked up by the noise pickup in front of the one of the multiple sound inlets be in conformity with the noise input from every sound inlet, but followings are its shortcomings:
1. As such noise-suppressing receiver with two series acoustic chambers belongs to open or semi-open one and has larger volume, and it is farther from the sound inlet of the pickup to ear root, the noise-suppressing receiver has good noise-suppressing effect only for the noises produced from the same side noise source. With the noises of the opposite side, because of sound velocity, a larger time difference between the time from the sound source to the sound inlet of the sound chamber and the time from the sound source to the ear root is produced. As a result, it will be difficult to simultaneously suppress noises from both sides of the environmental noises leaked from the ear root to the inner ear because it is impossible to make suitable and corresponding phase shift to the noise with different distance and sound intensity, which will cause bad effect for suppressing noise from either side.
2. The environmental noise input from the external sound inlet goes to the vibration diaphragm of the backside of the speaker only through internal sound inlet, instead of to the auditory meatus in front of the vibration diaphragm of the speaker. On the same time, it has to the selectivity to the frequencies passed, so it is a semi-open sound inlet channel and cannot cancel the environmental noise leaked from the gap between the edge of noise-suppressing receiver and the skin.
3. In order to reduce the probability that the echoes sounded from the receiver are re-picked up by the environmental noise pickup, the receiver is placed farther from the microphone, and there is a sound insulation cushion ring around the touch part between the ear enclosure and the skin of the ear root. Therefore, its volume is larger and its noise suppressing effect is not perfect yet
4. Because of larger volume, it is suitable only for head-wearing use and cannot be used for small-size noise-suppressing receiver, such as earphone, in-ear-phone, auditory meatus style or deep auditory meatus style phone.
When people are near to a high noise sound source, because the sound signal with high noise sound intensity will cover over other useful sound signals, it becomes necessary to develop a pickup that can attenuate the sounds produced by the sound source near the receiver and can receive the sounds produced by the farther sound source, in order than the person under such environment can hear the sounds produced by the sound sources around.